The CABC (Content Adaptive Backlight Control) module is a dynamic backlight adjustment module in a liquid crystal display, a PWM waveform outputted by the CABC module is communicated to a backlight driver circuit, since a voltage of the backlight driver circuit is about 20V, an operating voltage of the CABC module is 3.3V, there is a risk of burning the CABC module due to a large external voltage. In the prior art, when logic circuits in the CABC module have a dysfunction, the CABC module cannot continue to operate properly. Alternatively, when only a small part of logic circuits in the CABC module has a dysfunction, impact on the circuit is relatively small, but the chance for errors of such CABC module whose small part has a dysfunction increases.
When the CABC module ceases its functions due to abnormality of the logic circuits, such manner reduces utilization of the circuit. On the other hand, if continuing to use the CABC module whose small part of logic circuits has a dysfunction, it increases the CABC module's chance for errors when outputting the PWM waveform for controlling backlight brightness.